Program and Agenda

Abstract

INTERPLAY BETWEEN IRON- AND SULFUR- CYCLING MICROBIAL COMMUNITIES AND GEOCHEMISTRY ALONG ECOSYSTEM GRADIENTS IN THE INTERTIDAL MIXING ZONE OF A BEACH AQUIFER

Fe- and S-cycling microorganisms in mixing zones of coastal aquifers have the potential to significantly influence export of C, N, P, Fe, S, and heavy metals in submarine groundwater discharge (SGD). Little is known about the responsible microorganisms and how they interact among themselves and with environmental geochemistry. Mixing zones host gradients of salinity, dissolved oxygen, and reduced Fe and S species, influencing the microbial community distribution and vice versa. An integrated geochemical and microbiological analysis will lead to a better understanding of the mechanisms affecting the SGD chemistry. We sampled pore water, surface sediments, and worm burrows monthly from a transect along an intertidal groundwater mixing zone at Cape Henlopen, Delaware. Utilizing several techniques, including cyclic voltammetry, the geochemistry of the mixing zone was monitored and compared to microbial community distributions. Shallow communities were dominated by heterotrophs. Sulfate-reducers (Desulfobacterales) and iron-oxidizers (Zetaproteobacteria) occurred deeper, and correlated with the distribution of reduced Fe and S species along groundwater flow paths. These microbial metabolisms lead to the precipitation of FeS and iron oxides that capture solutes, controlling SGD chemistry.

Authors

McAllister, S. M., University of Delaware, USA, mcallis@udel.edu

Barnett, J. M., University of Delaware, USA, barnett@udel.edu

Luther III, G. W., University of Delaware, USA, luther@udel.edu

Michael, H. A., University of Delaware, USA, hmichael@UDel.Edu

Chan, C. S., University of Delaware, USA, cschan@udel.edu

Details

Oral presentation

Session #:060
Date: 2/25/2014
Time: 09:00
Location: 316 B

Presentation is given by student: Yes